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https://issues.apache.org/jira/browse/HIVE-27296?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated HIVE-27296:
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Labels: pull-request-available (was: )
> HiveRelDecorrelator does not handle correlation with Values
> -----------------------------------------------------------
>
> Key: HIVE-27296
> URL: https://issues.apache.org/jira/browse/HIVE-27296
> Project: Hive
> Issue Type: Bug
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> The {{HiveRelDecorrelator}} does not cope well with {{Values}} expressions
> and when such expression exists in the plan it fails to remove the respective
> {{{}Correlate{}}}.
> In HIVE-27278, we discovered a query that has a correlation over an empty
> {{Values}} expression.
> {code:sql}
> EXPLAIN CBO SELECT id FROM t1 WHERE NULL IN (SELECT NULL FROM t2 where t1.id
> = t2.id);{code}
> The CBO plan after decorrelation is shown below.
> {noformat}
> HiveProject(id=[$0])
> LogicalCorrelate(correlation=[$cor0], joinType=[semi], requiredColumns=[{}])
> HiveTableScan(table=[[default, t1]], table:alias=[t1])
> HiveValues(tuples=[[]])
> {noformat}
> Although, in HIVE-27278 we could find a solution for a plan that contains an
> empty {{Values}} there can be queries with correlations on non-empty
> {{Values}} and for those we don't have a solution at the moment.
> Normally after decorrelation we shouldn't have any {{Correlate}} expressions
> in the plan.
> The problem starts from
> [HiveRelDecorrelator.decorrelate(Values)|https://github.com/apache/hive/blob/59058c65457fb7ab9d8575a555034e6633962661/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java#L471]
> that returns null when it encounters the {{Values}} expression.
> Later, in
> [HiveRelDecorrelator.decorrelate(Correlate)|https://github.com/apache/hive/blob/59058c65457fb7ab9d8575a555034e6633962661/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java#L1247]
> it will bail out when treating the {{Correlate}} since one of the inputs is
> not rewritten.
> The problem is still there in latest Calcite (CALCITE-5568).
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